Humidity and Moisture Pests: What to Watch For in Ontario

Why are millipedes and sowbugs coming into my house?

Look for moisture: Health Canada says a persistent infestation of sowbugs, pillbugs or millipedes indoors may indicate a serious moisture problem in the home. Millipedes and sowbugs are the ones you notice first when it's wet. Sowbugs and pillbugs can sometimes enter damp areas of a house in large numbers, Health Canada says, while millipedes do not survive once inside because the home is too dry for them.

Health Canada also says these creatures are not harmful, and suggests making sure the ground slopes away from the house and using coarse mulch that lets water drain.

When do earwigs and cluster flies move into Ontario homes?

Earwigs may begin to wander into homes in June or July, Health Canada says, while cluster flies move into wall voids and attics to spend the winter. During the day, Health Canada adds, earwigs hide in cool, dark, moist places such as under stones and in garden rubbish. A 2022 review in The Canadian Entomologist says several hundred cluster flies may gather in any one cluster, entering cracks in the walls and roofs of houses to overwinter.

Why are there bugs in my damp basement?

Damp basements draw moisture-loving bugs such as silverfish, which Health Canada says prefer 75 to 95% relative humidity, so the fix is drying the space as well as treating the pests. Health Canada also lists bathrooms and wall voids among the places silverfish are often found. Moisture also promotes the growth of mould inside the house, and Health Canada advises keeping indoor relative humidity between 30% and 50%.

After a wet season, check your basement, crawl space and the outside of your foundation. Fixing damp spots in the fall, before pests go looking for winter shelter, is one of the cheapest ways a homeowner can keep them out.